This grant application proposes to test the hypothesis that aging in related to lipid peroxidation damage through either in increased rates of cellular lipid peroxidation or through decreased "antioxidant protective capacity of the cell." The author proposes to focus on the isolated hepatocyte as the central model for his studies though he will conduct some similar studies on hepatocytes in culture and subcellular organelles. The isolated hepatocyte is proposed as the primary model because it allows the use of an isolated metabolically active entity comparable to intact liver but free from influences difficult to control. The author proposes to study his hypothesis by, 1) establishing the structural and functional intactness of the isolated hepatocytes; 2) evaluating the levels of lipid peroxidation and 3) the susceptibility to induced lipid peroxidation injury; 4) evaluating the capacity of hepatocytes to prevent lipid peroxidation damage, and 5) attempting to alter the rates of lipid peroxidation in hepatocytes (either increasing or decreasing it by dietary manipulation) to observe changes in the susceptibility of isolated hepatocytes to lipid peroxidation injury.